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April 18, 2003

Christmas Tree Scouting Report -
Number 4

Welcome to the Christmas Tree Scouting Report for the week ending April 18. The next report will be available after 4 PM on Friday April 25. To receive a FAX of this week's message, please call (814) 865-1636. To report pest activity at your location or request the email report, please call 717 772-5229. 

What a difference in the weather this week compared to last. The week started out beautifully, giving growers a chance to get their seedlings planted and, hopefully apply some chemical controls. There was a lot of white pine weevil activity this week in Columbia, Dauphin, Lebanon, Luzerne, Northumberland and Perry counties. A few eggs were found in white pine terminals in Columbia and Perry counties. In Dauphin, Lebanon, Luzerne and Northumberland counties adults and feeding damage were observed on white pine, but no eggs were located. However, in Lebanon County, adult feeding damage to Norway spruce was noticed and when the terminals were examined closely, eggs were found. Growers must remember that this weevil is capable of destroying several years of terminal growth on eastern white pine, all spruce species, Douglas fir and occasionally true firs. Besides using a registered insecticide labeled for any pest, timing and good coverage are necessary for getting optimal control. Only the top 1/3 of the trees should be sprayed when white pine weevils or their spring feeding damage is noticed. Once eggs hatch under the bark of the terminals, the larvae cannot be controlled with chemicals. They must be cut out. If you have not applied your 1st spray for white pine weevil, do so as soon as possible to prevent further damage.

Cooley Spruce gall adelgids on the underside of Douglas fir needles in Columbia, Lebanon and Northumberland counties are beginning to produce wax over their entire body. Soon, long waxy filaments will completely cover this maturing female and she will begin to lay egg. In Columbia County, maturing females of eastern spruce gall adelgid are covered with masses of white, cottony wax. They are easy to see on the branches, near the terminal buds. No eggs were found. This indicates the window for control is ending and the next time to control this insect pest will be in the fall, after damage has been done to the trees.

The overwintering eggs of the balsam twig aphid are close to 90% hatched in Berks, Columbia, Dauphin, Lebanon and Northumberland counties. If you grow a variety of true firs, you already know that certain varieties break bud before others. It is a good practice to monitor those earlier varieties and begin spraying closer to bud break to insure all overwintering eggs of this aphid pest are hatched.

Eriophyid mites have been found on Blue and Norway spruce at many locations already this year. These minute mites are known to cause significant damage in the form of bronzing or russeting of the needles. When populations are extremely high, control is warranted. Although not controlled by traditional miticides, these unique mites are easily killed with oil or formulations of carbaryl. But remember, two applications are necessary to control those mites not eliminated by the 1st spray. Light populations of eriophyids on true firs are noticed from time to time, but a population high enough to cause damage is unusual in Pennsylvania. This week in Dauphin County, high populations of hemlock rust mite were found on Concolor fir and damage to last year's growth was evident. In North Carolina, hemlock rust mite is a serious pest on Fraser fir. But, in Pennsylvania the common eriophyid on Fraser fir is a related species, Nalepella octonema. This species does not have a common name but may be referred to as the fir rust mite. Rarely have we seen damage from this fir rust mite.

Male and female cones are beginning to form on Douglas fir in Berks and Lebanon County. Female cones tend to be closer to the top of the tree and stand up right, whereas male cones are on the lower branches. The male cones hang downward and are normally more plentiful. These unique looking structures are sometimes mistaken for galls or other insect or disease conditions. Cones were also noticed forming on balsam fir in Berks County.

Elongate hemlock scale overwintering eggs have not started to hatch on Fraser fir in Columbia County. This scale is also known to infest spruce and Douglas fir, but does not appear to cause significant damage to those hosts.

Another scale pest that we will be monitoring is Aspidiotus crytomeriae, the "cryptomeria scale". This scale has two crawler emergence periods per season, the first usually in early June and the second in early September. This scale can be recognized by its oval covering. It has a golden yellow center, composed of cast skins, surrounded by gray-white waxy material secreted by the scale insect.

The next report will be available after 4 PM on Friday April 25th, 2003.